As dark net drug marketplaces continue to pop up, law enforcement agencies are playing a game of online whack-a-mole. Giving dark net sellers bad reviews and scores can be an effective way of keeping potential first-time buyers away, a new study suggests.

The increasing cost of pharmaceutical drugs is driving more people to the dark net, lead author Scott Duxbury, a doctoral student in sociology at Ohio State University, said in a phone interview. Officials use an array of methods to deter potential buyers from dark net drug marketplaces: Some have been known to exaggerate the number of crackdowns to appear more effective, for example. AlphaBay and Hansa, two of the biggest dark net marketplaces since the Silk Road, were shut down just last month.

Duxbury’s research, which was published in the Journal of Quantitative Criminology and is being presented Saturday in Montreal, analysed transactions involving opioids in dark net marketplaces between 57 sellers and 706 buyers. It found that first-time buyers, who made up 82 percent of users during the six months they conducted the study, valued trustworthiness of a seller—whether or not they had good reviews and scores, according to the authors’ methodology—more than how low their prices were.

Though it wouldn’t work for the smaller number of dedicated return buyers, the researchers’ solution would be to flood a seller’s page with bad reviews and scores so that inexperienced buyers won’t know where to go and who to trust. According to the paper, “the most effective way to curb Tor network drug trafficking may be to simply target emerging vendors’ reputation. For example, law enforcement may be able to make a few small transactions with emerging vendors and give negative evaluations.”

“It’s a low-investment effort to do something like that, and it stops the markets from growing in the first place,” said Duxbury.

The study found that only 18 percent of buyers returned to the marketplace for a second purchase, and once they found a seller they trusted, only 30 percent shopped around. This creates a solid internal network of established buyers and sellers that can be difficult to disrupt.

The other problem, according to Duxbury, is that the marketplaces don’t operate as separate entities, but as a growing interconnected network of sites. As opposed to a traditional drug trade, dark net marketplaces are less reliant on the connections of individual sellers, and are less affected by law enforcement takedowns, Duxbury said.

“In regular drug trade, there are key players that resources and connections are routed through. If you can take out those key players, you can really hinder the market,” he said. “But what we’re seeing here, there’s just a ton of other key players that can fill the void. So it doesn’t actually inhibit the activity that much.”